This application claims the priority of German Patent Application 103 35 216.3, filed Aug. 1, 2003, the disclosure of which is expressly incorporated by reference herein.
This invention relates to a phase-controlled antenna comprising a plurality of antenna elements situated in the area of the surface of a mobile device.
Trackable bundled antennas are required for transmission of large data volumes over great distances between unmanned flying devices, airplanes, motor vehicles and stationary stations. These antennas can automatically align themselves with the remote station in accordance with the rate of propagation of the respective device.
The use of mechanically pivotable or phase-controlled directional antennas, usually covered with large radomes, is possible only to a limited extent because of the considerable amount of space required, e.g., in compact flying devices. Essentially antennas in a stationary installation are preferred in comparison with mechanically movable antennas in mobile devices because of their lower sensitivity to high mechanical loads. Therefore, there has been increased development of phase-controlled antennas whose directional effect is variable without mechanical drives and which therefore can be positioned much more rapidly in the new direction. However, phase-controlled directional antennas are very complex because of the large number of component antennas required and because each component antenna must be triggered in a phase-controlled and amplitude controlled manner.
Phased-array antennas are generally known. U.S. Pat. No. 4,656,482 A1 describes a phased-array antenna that can be installed in the wing of a flying device. This antenna is designed for the same intended application but it requires a great complexity of components for controlling the individual active antenna elements because of the many antenna components which must be triggered in a phase-controlled and amplitude-controlled procedure. This type of antenna has an extremely broad band but controlled adjustability of the directional effect is limited, particularly in the elevation direction. Finally, a substantial extent is necessary in the base plane to generate the directional effect.
The object of this invention is therefore to design a phase-controlled antenna for installation in the area of an exterior surface of a mobile device, preferably a flying device, which avoids the aforementioned disadvantages of the known prior art, is characterized by a simplified design and electric control and can be designed to be more compact with regard to the planar extent without any restriction on the electric specifications.
In addition to the easy integrability into existing structures of mobile devices, the special advantage of the inventive phase-controlled antenna is also the small amount of space required in the plane in which the antenna elements are arranged. It is advantageous that only a small number of individual antenna elements is needed in a plane in comparison with the prior art. In addition, it is advantageous that two or more planes having a similar arrangement of antenna elements one above the other produce an additional improvement in the directional effect and thus increase the antenna gain in the elevation direction. With high-frequency signals it is advantageous that only the central active antenna element receives signals, whereas the alignment in the elevation direction and in the azimuthal direction is accomplished exclusively by control signals with the help of which the electrically active length of the passive antenna elements is varied. This eliminates the complex networks which are necessary in the conventional prior art for supplying signals in the correct phase sequence to individual antenna elements.
If the antenna is used for reception, it is advantageous that the efficiency of the antenna is high because there are no distribution networks or phase shifter networks whose losses would reduce the efficiency.
The individual antenna elements may optionally be designed as monopoles or dipoles in suitable embodiments. The coupling may be influenced through a suitable choice of the respective transverse dimension, i.e., the diameter of the antenna element and/or through the choice of the distance between the individual antenna elements, depending on the type of design.
The controlled adjustment of the phase effect of the individual passive antenna elements is accomplished easily by connecting or disconnecting and/or bridging the passive components (such as capacitors or inductors), by connecting or disconnecting controllable components (such as variable capacitance diodes or variometers) and by connecting lines. Control of the controllable components may be accomplished by analog or digital means using D/A converters.
To improve the directional effect in the elevation direction, two or more planes with the same groups of active and passive antenna elements are advantageously arranged one above the other with a distance of at least one-third of the operating wavelength being maintained between the ends of the antenna elements of different levels. The antenna diagram of the overall arrangement of the phase-controlled antennas in the elevation direction is advantageously accomplished by individual control of each plane with regard to the absolute value and phase of the signal. The distance between two levels should amount to at least ¾λ of the operating wavelength.
A phase-controlled antenna of the inventive design is very suitable for integration into the area of the contour of a mobile device, especially naturally for installation in aerodynamically active surfaces such as the wings, the horizontal stabilizer or the flaps of a flying device. It can be installed equally well in an aerodynamically shaped housing which is mounted at a certain distance from the contour of the actual flying device with the help of a stanchion. The maximum range of the usable directions for reception and emission of signals will then also vary, depending on the installation site.
The phase-controlled antenna may also be installed in the wing tip of a flying device, where the wing tips are pivotably mounted on the wing for pivoting about an axis aligned in the direction of flight so that the respective wing tip is always approximately in the horizontal during the flight.
Finally, an especially advantageous design of the antenna array is proposed in which additional strip-shaped plates which contain the antenna elements and the components required for controlling them are arranged perpendicular to a base plane, which may also be designed in multiple layers and may have multiple conductors or conducting surfaces.
Because of the compact dimensions, the radar localizability of the antenna is also reduced. Thus in the case of flying devices, defensive measures (e.g., flare jammers) against threats from the ground may also be greatly reduced. Furthermore, the localizability from the ground is reduced because signals are emitted only in the direction of the remote station. Because of the good bundling in the azimuth and elevation, the localizability from the ground is reduced because of the lower required transmission power, and because signals are emitted only in the direction of the remote station. This reduces the electric power to be supplied.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.